Additive products designed to provide enhanced oxidisable stain removal performance are known in the art. Most of these prior art additive products are granular in character and are intended primarily, if not solely, as adjuncts to conventional laundry detergent granules. Such additive products conventionally comprise a bleach or bleach precursor in admixture with a coating or carrier material which serves to enhance the stability of the bleach component and facilitates its uniform dispersion in the granular laundry detergent.
The incorporation of peroxy bleach precursors (hereinafter referred to as bleach activators) into granular additive products is also the subject of numerous prior art disclosures, examples of such disclosures including German Patent Applications DT OS 2650429 and 2651254 and British patent specification Nos. 1,441,416, 1,398,785 and 1,395,006. In general, these disclosures teach the incorporation of a fine particulate peroxy bleach activator, optionally with additional stabilising compounds, into a larger agglomerate, using organic solids having melting points in the range 30.degree.-60.degree. C. as the agglomerating agents.
In all of these prior art disclosures the primary objective has been the formation of a bleach additive granule containing a peroxy bleach activator whose chemical stability could be maintained in a hostile environment eg. during storage under conditions of high temperature and humidity in intimate contact with an alkaline peroxy bleach-containing detergent.
In order to achieve this objective one or other of two techniques has been adopted. In one technique, relatively large quantities (viz. up to 50% by weight of the additive) of one or more non-hygroscopic, sparingly water-soluble or insoluble organic solids of the desired melting point range have been used to form a matrix within which the peroxy bleach activator is dispersed. This provides a particle having acceptable storage stability but requires the incorporation of a significant amount of a non-functional diluent in the product and also imposes limitations on the rate of solubility in aqueous media, particularly at low temperatures.
The other technique has employed a low level (viz. 5-20% by weight of the additive) of agglomerating agent as a binder to hold particles of bleach activator together, for which purpose a wider range of materials has been found acceptable, including the water soluble ethoxylates of higher fatty alcohols and alkyl phenols whose hygroscopicity can be tolerated at low levels of usage.
The use of this technique has minimised the level of diluent, albeit with some sacrifice of the stability of the bleach activator, but at the same time the low level of agglomerating agent has rendered it ineffective for any other purpose even when a surfactant material having detergent functionality has been employed.
In both of these approaches the objective has been to provide a particulate additive product compatible with conventional granular laundry detergents. Although this requirement imposes limitations on the product from the standpoint of chemical stability it does render the flow characteristics of the product less important because advantage can be taken of the good flow characteristics of the base granular detergent. Nevertheless the use of major amounts of hygroscopic materials, such as detergent-functional nonionic surfactants, as agglomerating agents in bleach additive products does lead to both flow and chemical stability problems, if such products are incorporated into conventional laundry detergents.
The additive compositions of the present invention however are not intended to form an integral part of a detergent composition ie. to be stable in intimate mixtures therewith over long periods of storage such as arise during distribution, sale and use of detergent products. The additive products of the present invention are intended to be manufactured and sold as such for use alone or for admixture with conventional detergents at the point of use. In consequence the additive compositions of the present invention need to combine chemical stability, high solubility and good granular flow characteristics.
The present invention seeks, as one of its objectives, to resolve these conflicting requirements by providing a matrix of materials in a particulate form that has satisfactory stability and rate of solution characteristics as made, and packaging the particulate mass so as to restrict the pick-up of moisture to very low levels. The invention also seeks to provide a product having a stain removal capability extending beyond oxidisable stains to greasy oily stains and, in preferred embodiments, to stains susceptible to chemical attack by means other than bleaching.